Br H. LEIGHTON KESTEVEN. 287 



dorsal edge; the posterior end is flattened and was attached to a 

 plank. Both siphons are well developed; the branchial is the 

 larger. The branchial siphon is seven-lobed, and between the 

 bases of the lobes are seven short brown lines. The atrial siphon 

 is five-lobed. 



The test is cartilaginous, thin and transparent, tinged green and 

 3'ellow. The body within is clearly visible through the test. 

 Test-cells are numerous; stellate (rare) and fusiform types are 

 present. Bladder cells are present in fair abundance, but vessels 

 and pigmented cells are absent. 



The mantle is delicate, translucent, and does not adhere to the 

 test except in the siphons. There is an irregular network of 

 muscle-bands on the left side and anteriorly between the siphons. 

 The branchial sac (Pis. xxv., figs. 7-8; xxvi., fig. 9) is fairly 

 strong and quite devoid of folds. Its general appearance is well 

 shown in the microphotograph (PL xxvi., fig. 9); the details are 

 complex. The transverse vessels given off from the ventral 

 sinus branch and anastomose to form a complex network 

 (PI. xxv , tig.7); all these are in one plane on the outer 

 side of the sac. The interstigmatic vessels are spirally coiled, 

 and the vortices are conical, their apices directed inwards. 

 In a plane just above, within, that of these apices there is another 

 reticulation of vessels, all of finer calibre than those of the outer 

 network. The most regularly arranged members of this inner 

 reticulum are transverse vessels, usually, though not constantly, 

 equidistant. These inner transverse vessels are not arranged in 

 any constant relation to the voitices; sometimes (PI. xxv., fig.8) 

 they pass on either side, at others across the centre of the vortex. 

 The fine irregular vessels given off from these pass to the interstig- 

 matic vessels or anastomose among themselves. The internal 

 longitudinal vessels are quite regular in their arrangement, and 

 are related to tlie inner transverse vessels exactly as depicted in 

 the figure (Plate xxv., fig.8). The meshes of the outer reticulum, 

 may contain two, three, or even four vortices, usually only one. 



The endostyle, commencing beyond the oesophageal aperture,, 

 sweeps round the sac without undulations. The circumoesophageal 

 bands have an even curv^e. 



